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Post-natal Macro- and Microscopic Changes of the Thymus of Sonali Chicken in Bangladesh

Ummay Ayman
Department of Anatomy and Histology, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, Bangladesh

Md. Rafiqul Alam
Department of Surgery and Obstetrics, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, Bangladesh

Shonkor Kumar Das
Department of Anatomy and Histology, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, Bangladesh

Abstract/ Executive Summary:

Avian lymphatic system plays a very significant role in immunity as well as disease control. This research aimed to investigate the histomorphological changes and involution of the thymus of Sonali chicken at different post-natal stages in Bangladesh as the age-related changes of the thymus of Sonali chicken were not described before. Materials and methods: A gross and microscopic investigation was performed on the thymus of 25 healthy Sonali chickens representing different stages of post-natal life: days 1, 14, 28, 42, and 56. Experimental chickens were sacrificed by cervical subluxation, and the thymus was collected and subjected for both the gross and histological studies. The histological changes were examined with light microscopy after H&E staining. Results: The thymus was located in close association of the jugular vein, having a long chain of thymic lobes, 5–8 lobes on each side. The statistically significant age-related changes were observed (p < 0.05). All gross parameters (weight, length, width, and thickness) found to be increased up to day 42. On day 56, the growth was found to decline from the previous groups. The microscopic observations revealed the same pattern of changes such as gross parameters, i.e., continuously increased till day 42 and then declined (p < 0.05). At day 56, the involutory signs such as partial loss of interlobular septa and accumulation of adipose tissue in connective tissue septa were found. Conclusion: It is well known that in chicken, after a certain period, the thymus got involuted. In Sonali chicken of Bangladesh, the age of involution was notified at day 56/8th week of the post-natal stage, which was correlated both in macro- and microscopic observations.

Keywords: Histomorphology; Involutory signs; Post-natalstage; Sonali chicken; Thymus

Location: Bangladesh Agricultural University (BAU) Poultry Farm, Mymensingh-2202, Bangladesh

Start Date:

End Date:

Program Area: Animal Health and Management

Commodity: Chicken

Objectives:

This research aimed to investigate the histomorphological changes and involution of the thymus of Sonali chicken at different post-natal stages in Bangladesh as the age-related changes of the thymus of Sonali chicken were not described before.

Methodology:

The experimental birds were sacrificed humanely following the ethical and welfare guidelines set by the Animal Welfare and Experimental Ethics Committee of Bangladesh Agricultural University [approval number: AWEEC/ BAU/2019(30)]. Sonali chicken- The experimental Sonali chickens (male chickens) were reared in Bangladesh Agricultural University (BAU) Poultry Farm, Mymensingh-2202, Bangladesh, with proper hygienic conditions, food and water ad libitum with strict biosecurity. Feeding history, vaccination schedule, and management practices of the chicken were taken into consideration. The collected chickens were free from any developmental disorder or detectable diseases. A total number of 25 (N = 25) chickens were used for the experiment and were divided into five age groups: day old, 14th day, 28th day, 42nd day, and 56th day; each group contained five chickens (n = 5). Chickens from each group were sacrificed by the cervical subluxation method. Then, the thymus glands were collected for gross morphometrical and histological evaluation. The investigation was performed in the Department of Anatomy and Histology, Faculty of Veterinary Science, BAU, Mymensingh-2202, Bangladesh. Morphometric study- After collection, the samples were weighed (gm) and measured for length, width, and thickness of the thymus by slide calipers. The color of the samples was recorded by eye estimation. The unit of length, width, and thickness measurement was millimeter (mm). The gross anatomical images were captured directly from the organs by using a digital camera. Histological study For histological observation, the thymus was preserved in Bouin’s fluid for 24–36 h. Then, the samples were washed in phosphate-buffered saline for three changes 20 min in each, dehydrated through ascending grade of alcohol (i.e., 70%, 80%, 90%, 100% (1), 100% (2), and 100% (3) alcohol) for 2 h in each, cleaned in xylene for 3 changes of 2 h in each, and finally embedded in paraffin. The paraffin blocks were cut at 6-μm thickness with a rotatory microtome. The microscopic study was facilitated by Harris’s Hematoxylin and 1% Eosin Y stain and finally mounted with Dibutylphthalate Polystyrene Xylene (DPX). Images of the microscopic structure of the thymus were taken by using a Carl-Zeiss Photo Microscope (Germany) connected with a digital camera. The histological parameters of thymic lobule (length, breadth, and thickness of the cortex and breadth of the medulla) were measured using a precalibrated ocular micrometer. Statistical analysis- The analysis of the collected data was performed using the Statistical Package for the Social Sciences (SPSS; version 22.0) software. The post hoc Duncan’s test was performed following one-way analysis of variance to analyze gross and histological parameters of thymus. The results were displayed in the form of mean ± mean of the standard error. In case of p values ranging below 0.05, the differences were considered to be statistically significant [14,15].

Source of Information: JOURNAL OF ADVANCED VETERINARY AND ANIMAL RESEARCH, VOL 7, NO. 2, PAGES 324–330, 2020

Article Link (Online Journal): http://doi.org/10.5455/javar.2020.g425

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Finally, evidence showed that morphometric changes are well correlated with the histological modifications. During post-natal growth and development of the thymus of Sonali chicken, some structural differences have been identified. Moreover, the age of involution is found at day 56 or 8th week of post-hatch age. The involutory signs include the loss of a clear distinction between cortex and medulla, partial loss of interlobular septa, accumulation of adipose tissue in connective tissue septa, and the number of Hassall’s corpuscles largely increased in the medulla. Moreover, the further study is required for molecular detection and immunological activities of the thymus in Sonali chicken.

Knowledge Management: Journal